Knee reflexes, also known as the patellar reflex, are a type of reflex action that occurs when the knee is tapped. This reflex is an example of a monosynaptic reflex arc, which involves only one synapse between the sensory and motor neurons. The knee jerk reflex is used by medical professionals to assess the health of the nervous system. The term 'JERKS' is often used to describe the sudden movement of the leg in response to the tap.